Proper Watering

• The first step to getting rid of soil gnats is to water your plants properly; most importantly, don't overwater them. Moist soil is what attracts soil gnats that are ready to lay eggs, so if you water your plants only when they need it, the soil is relatively dry most of the time. This will keep the soil gnats away and your plant's root systems safe.
  
  

Sand

• If you've been overwatering your plants without realizing it and you've already got soil gnats that are causing damage, the solution is sand. Let your soil dry out completely, then sprinkle about a 1-inch layer of sand over the soil. Because sand will drain water fast, it will make the adults think the soil is dry and they won't lay their eggs in it.
  
  

No Peat

• Potting soil that has peat as an ingredient tends to attract soil gnats. So you can avoid getting soil gnats by using no soil with peat in it. Instead, use a soil mixture that has vermiculite and perlite. If you've been using soil that has peat, consider replanting all your plants in soil that doesn't have any. While time-consuming, it will help eliminate soil gnats and their larvae.
  
  

Sticky Trap

• If you've got adult soil gnats they are becoming bothersome, you can get rid of them with homemade sticky traps. Soil gnats are attracted to yellow, so coat a sheet of yellow paper with vaseline and hang it close to the gnats. Many of them will be attracted to it and get stuck on your homemade trap.
  
  If you follow the other three tips, too, you should end up with no soil gnats at all.